According to the newspaper, it reads: "We submit that all of the victims were under the control and authority of the UK at the times of the deaths and ill-treatment.

"The four boys killed all appear to have been deliberately targeted at close range by British forces. All were killed in a residential area over which UK forces clearly had the requisite degree of control and authority."

The deaths, on October 18 in the village of Loi Bagh in Nad Ali, Helmand province, have previously ben explained as the “killing of four Taliban enemies in action”.

Tessa Gregory, lawyer for the brother of two of the dead teenagers Noor Mohammad Noorzai, told the Guardian she had obtained signed statements from witnesses who contradicted that version of events.

She said: "On 18 October 2012, during a joint British-Afghan security operation, four innocent Afghan teenagers were shot whilst drinking tea in their family's mud home in Helmand province.

“Our client, the elder brother of two of the teenage victims, wants to know why this happened

“We hope that in light of our urgent representations the Ministry of Defence will act swiftly to ensure that an effective and independent investigation is carried out without any further delay.”

A spokesman for the MoD said: "The Ministry of Defence received details of these allegations on Tuesday in a letter from a UK firm of solicitors on behalf of an Afghan national and will give them full consideration before responding.

“The 'letter before action' is the first stage of seeking a judicial review and requires the MoD to reply within 14 days, providing a reasonable opportunity to consider the claim and whether there is a case to answer."

He added the protection of the Afghan civilian population is at the core of the International Security and Assistance Force’s military strategy in Afghanistan.